It is frequently desired to remove materials from over substrate surfaces. For instance, semiconductor fabrication may involve removal of contaminant particulates from over a semiconductor substrate surface, and/or stripping of sacrificial materials from over a semiconductor substrate surface. The terms “semiconductive substrate,” “semiconductor construction” and “semiconductor substrate” mean any construction comprising semiconductive material (for instance, silicon and/or germanium), including, but not limited to, bulk semiconductive materials such as a semiconductive wafer (either alone or in assemblies comprising other materials), and semiconductive material layers (either alone or in assemblies comprising other materials). The term “substrate” refers to any supporting structure, including, but not limited to, the semiconductive substrates described above.
Numerous cleaning solutions and chemistries have been developed for removing materials from over semiconductor substrate surfaces. The cleaning solutions may, for example, comprise deionized water. The water may be utilized alone, or in combination with one or more of sulfuric acid, hydrochloric acid, hydrofluoric acid, ammonium hydroxide, hydrogen peroxide, etc. Accordingly, cleaning solutions may be acidic, basic, or of neutral pH, depending on the application.
Some materials are fairly easy to clean from over semiconductor substrates, in that the materials are chemically much different than the underlying surface of the semiconductor substrate. However, other materials can be difficult to remove selectively relative to an underlying surface of a semiconductor substrate in that the materials may be of the same composition, or of a similar composition, as one or more regions of the surface of the semiconductor substrate. Materials that can be particularly difficult to remove in some applications are silicon, silicon dioxide, silicon nitride, and polymeric organic materials.
A method being developed for removal of materials is to utilize liquid aerosol particles (which may also be referred to as clusters) to impact a surface of a semiconductor substrate and dislodge undesired materials from such surface. The liquid aerosol particles may dislodge the materials by physical interaction (analogous to bead-blasting), chemical interaction (in other words, reaction with the materials to convert them to a form more readily dislodged than an initial form), or a combination of physical interactions and chemical interactions. In some applications, the liquid aerosol particles may be charged so they have a polarity (either positive or negative), and the liquid aerosol particles may impart such polarity to the undesired materials on the substrate surface. The substrate may be charged to the same polarity as that imparted to the undesired materials so that electrostatic repulsion occurs between the substrate surface and the undesired materials to assist in dislodging such materials from the surface.
The liquid aerosol particles may be formed by passing liquid to an aerosol generator. The aerosol generator may be an aerosolizing (or atomizing) nozzle or spray head, such as, for example, an electrostatic nozzle, a piezoelectric nozzle, an ultrasonic or megasonic nozzle, or an electrohydrodynamic atomization nozzle. The term “aerosol” means a suspension or dispersion of fine particles (which may be referred to as clusters or droplets in some embodiments). The term “liquid aerosol particle” means aerosol particles that are primarily of a liquid phase, and is synonymous with the term “aerosol droplet”. The liquid aerosol particles may have a volume of less than three picoliters; may have a mean size distribution of less than 10 microns, and in some applications may have a mean size distribution of less than 100 nanometers.
The liquid aerosol particles may be directed toward a substrate surface via any suitable method, including, for example, spraying (fluid force propulsion), gas jet, electrostatic forces, etc.
Although aerosols have potential for utilization in cleaning various substrates, such as semiconductor substrates, they currently have limited application. It is desired to develop improved methods for cleaning substrates, such as semiconductor substrates, which improve applicability for utilization of aerosols in diverse applications.